As if falling 2-1 to Watford wasn't enough of a blow to Arsene Wenger, Arsenal may have to deal with further injury layoffs for two star players.

Per Mertesacker headed the Gunners ahead with his first league goal in 1400 days, only for a contentious Troy Deeney penalty to draw Watford level before Tom Cleverley's late heroics sealed a memorable 2-1 victory.

And to make matters worse, Danny Welbeck and Laurent Koscielny both failed to finish the game at Vicarage Road.

A disappointed Wenger offered an update after the match.

“It looks to be a hamstring with Welbeck,” Wenger said.

“I don’t really know because everybody is shocked in the dressing room [about the result]. It looks a muscular problem.

“Koscielny is a muscular problem as well.”

Welbeck is escorted from the pitch by the medic (Image: Getty Images Europe)

Laurent Koscielny made a welcome return to the starting line-up but didn't finish the match (Image: Getty Images Europe)

Arsenal started without either Mesut Ozil or Alexis Sanchez having won their last four games in all competitions following a slow start but they were poor for much of the contest.

A point would have seen Arsenal leapfrog Chelsea into fourth but it was Marco Silva who was instead left toasting a place in the top four.

Wenger made four changes as Mertesacker and Koscielny came into the back three, with Shkodran Mustafi injured on international duty and Rob Holding named as a substitute.

Both Aaron Ramsey and Sanchez were left out completely due to fatigue, with Ozil only named on a strong Arsenal bench.